1. Field of the Invention
The present invention relates to a scroll compressor, and more particularly to, an apparatus for varying a capacity of a scroll compressor which can vary a capacity of a refrigerant compressed using a high pressure in a casing.
2. Description of the Background Art
Generally, a scroll compressor comprises: a motor mechanism mounted in a casing and for generating a rotary force; and a compression mechanism for sucking, compressing and discharging gas by receiving a driving force from the motor mechanism while a orbiting scroll is orbiting engaged with a fixed scroll.
The scroll compressor is classified into a low pressure scroll compressor in which a casing is kept in a low pressure state and a high pressure scroll compressor in which a casing is kept in a high pressure state.
In the low pressure scroll compressor, a refrigerant gas having passed through an evaporator is let into a casing, the gas let into the casing is sucked into a compression mechanism, compressed and discharged, and the refrigerant gas of high temperature high pressure state discharged from the compression mechanism is discharged to a condenser side through a discharge pipe. Due to this, the casing maintains a low pressure state.
Such a low pressure scroll compressor is provided at the tips of a fixed scroll wrap and of a orbiting scroll wrap with tip chambers for preventing gas leakage, thereby preventing the leakage of gas compressed between compression pockets formed by the fixed scroll wrap and orbiting scroll wrap.
In the high pressure scroll compressor, a refrigerant gas having passed through an evaporator is sucked directly into a compression mechanism and compressed, and the refrigerant gas compressed in the compression mechanism is discharged into a casing. The refrigerant gas of high temperature and high pressure state discharged into the casing is discharged to a condenser through a discharge pipe. Due to this, the casing maintains a high pressure state.
Such a high pressure scroll compressor is provided at the tips of a fixed scroll wrap and of a orbiting scroll wrap with no tip chambers for preventing gas leakage, and thus prevents the leakage of gas compressed between compression pockets formed by the fixed scroll wrap and orbiting scroll wrap by using a pressure of the casing of high pressure state.
FIG. 1 is a front sectional view illustrating one example of a compression mechanism of a high pressure scroll compressor. FIG. 2 is a plane view illustrating a fixed scroll wrap and a orbiting scroll wrap constituting the compression mechanism.
As illustrated therein, the compression mechanism of the scroll compressor comprises: a fixed scroll 30 mounted in a casing 10 at a predetermined gap from a main frame 20 mounted in the casing 10; a orbiting scroll 40 located between the fixed scroll 30 and the main frame 20 so as to be swivellingly engaged with the fixed scroll 30; and an Oldham's ring 50 located between the orbiting scroll 40 and the main frame 20 and for preventing the rotation of the orbiting scroll 40. The orbiting scroll 40 is connected to a rotary shaft 60, the rotary shaft being coupled to a motor mechanism.
The main frame 20 includes a frame body portion 21 having a predetermined shape, a shaft insertion hole 22 formed at the frame body portion 21 and for having the rotary shaft 60 penetrated and inserted thereinto, a boss insertion groove 23 extending from the axial insertion hole 22 and having a larger inner diameter than the shaft insertion hole 22 has, and a bearing surface 24 formed on the top surface of the frame body portion 21 and for supporting the orbiting scroll 40.
The fixed scroll 30 includes a body portion 31 formed in a predetermined shape, a wrap 32 formed on one surface of the body portion 31 in an involute curve having a predetermined thickness and height, a discharge opening 33 penetrated at the center of the body portion 31, and a suction port 34 formed at one side of the body portion 31.
The orbiting scroll 40 includes a disc portion 41 having a predetermined thickness and area, a wrap 42 formed on one surface of the disc portion 41 in an involute curve having a predetermined thickness and height, and a boss portion 43 formed at the center of the other side of the disc portion 41.
The orbiting scroll 40 is coupled between the fixed scroll 30 and the main frame 20 so that the wrap 42 is engaged with the fixed scroll wrap 32, the boss portion 43 is inserted into the boss insertion groove 23 of the main frame 20 and one surface of the disc portion 41 is supported by the bearing surface 24 of the main frame 20.
The rotary shaft 60 is penetrated and inserted into the shaft insertion hole 22 of the main frame 20 to be coupled to the boss portion 43 of the orbiting scroll 40.
A suction pipe 12 for sucking gas is penetrated and coupled to the casing 10, and the penetrated suction pipe 12 is coupled to the suction port 34 of the fixed scroll. And, a discharge pipe 13 for discharging gas is coupled to the casing 10.
Unexplained reference numeral B represents bushes and 62 represents an oil flow passage of the rotary shaft.
The operation of the compression mechanism of the high pressure scroll compressor as set forth above will be described below.
Firstly, when the rotary shaft 60 rotates by a rotary force transmitted from the motor mechanism, the orbiting scroll 40 coupled to an eccentric portion 61 of the rotary shaft swivels around the axis of the rotary shaft 60. The orbiting scroll 40 swivels as being prevented from rotation by the Oldham's ring 50.
With the orbiting scroll 40 orbiting, as the wrap 42 of the orbiting scroll swivels engaged with the wrap 32 of the fixed scroll, a plurality of compression pockets P formed by the wrap 42 of the orbiting scroll and the wrap 32 of the fixed scroll moves to the center parts of the fixed scroll 30 and orbiting scroll 40, and at the same time, as their volume changes, sucks and compresses gas and discharges it through the discharge opening 33 of the fixed scroll.
At this time, the refrigerant sucked through the suction pipe 12 is directly let into the compression pockets P through the suction port 34 of the fixed scroll, and the refrigerant of high temperature and high pressure state discharged through the discharge opening 33 of the fixed scroll passes through the casing 10 and is discharged to the outside through the discharge pipe 13.
The compression pockets P are continuously formed as the orbiting scroll 40 swivels. If the compression pockets P are located at the edge of the fixed scroll 30, they are in a low pressure state, which is a suction pressure. If the compression pockets P are located at the center of the fixed scroll 30, they are in a high pressure state, which is a discharge pressure. If they are located halfway between the edge and center of the fixed scroll 30, they are in an intermediate pressure state.
The inside of the casing 10 is always maintained in a high pressure state. By such a high pressure in the casing 10, a high pressure is applied to the back of the disc portion 41 of the orbiting scroll and thus the tip faces of the fixed scroll wrap 32 and orbiting scroll wrap 42 are closely contacted to the inner surface of the fixed scroll 30 and the disc portion 41's surface of the orbiting scroll, thereby preventing a pressure leakage between the compression pockets P formed by the wrap 42 of the orbiting scroll and the wrap 32 of the fixed scroll.
Meanwhile the aforementioned scroll compressor constitutes a cooling cycle system, and the cooling cycle system including the scroll compressor is mainly mounted to an air conditioner or the like. Upon operating the air conditioner, in order to minimize the power consumption of the air conditioner, there is a need to vary the capacity of the scroll compressor operating the cooling cycle system mounted to the air conditioner.